1. Field of the Invention
The invention relates to real-time automatic systems for performing welding operations and more particularly to an improved computerized system for translating a torch head tip at a constant speed along a contoured path extending in a direction generally common, but not necessarily similar, to the surface of an adjacently related elongated workpiece of a contoured configuration.
One of the numerous problems encountered in automatically welding parts which are neither straight nor uniformly round is that geometric relationships existing between the welder and the part to be welded can cause large variations in weld speed to occur. Unless, of course, counter measures are taken, these variations often result in nonuniform weld nuggets with an attendant loss of reliability. Since in most automatic commercial welding systems power supplies and controls are designed to maintain constant current, voltage, and travel speed, the welding of a straight or round piece does not present a control problem simply because the heat applied in watts per centimeter of weld length is a constant value. However, if a part to be welded is neither straight nor uniformly round, the surface speed of the torch tip usually will not be constant. A weld joint which is straight and progresses into a curved section is especially susceptible to weld-speed error. The same is true of elliptical bulkheads.
2. Description of the Prior Art
Computerized weld skates with torch angle and weld-speed control heretofore have been employed with varying degrees of success. Such systems are shown and described in U.S. Pat. Nos. 3,443,732 and 3,469,068.
While the patented systems aforementioned have performed satisfactorily for their intended purpose, generally speaking it has been found that certain disadvantages are encountered when employing these systems. For example, in the weld skate described in U.S. Pat. No. 3,469,068, the torch tip tends to exhibit instability whenever the rollers supporting the skate cross a joint in the skate track. Apparently, this perturbation is caused by the three-point wheel trucks which tend to move in an unpredicted manner and is multiplied by cantilever action of the torch head. The result is unwanted movement of the torch head along, and perpendicular to, the plane of the weld joint. Additionally, the system also includes a track radius transducer which is used to measure the instantaneous radius of the skate track. Consequently, the system is extremely sensitive and suspect of being inaccurate. Moreover, the system necessarily is expensive to fabricate, maintain and operate.
Additionally, numerically controlled welding systems requiring hard, fixed X, Y and Z axis reference points to maintain accuracy have been employed, also with varying degrees of success.
A primary disadvantage of numerical control welding machines, of course, is the high cost of precision tooling required to establish the X, Y and Z axis reference points and the large engineering cost of programming and verifying each different weld configuration prior to production. Moreover, a numerical control welding tool is by design necessarily limited in the size of workpiece it can process.
It is, therefore, the general purpose of the instant invention to provide an improved computerized welding system including a subsystem operable to translate a torch tip at a constant travel speed and torch angle along a contoured track, in accordance with real-time outputs of a digital computer control circuit.